Lena Dunham's usually brown-haired costar has followed in her platinum blonde footsteps with a brand new (much lighter) hairstyle. Zosia Mamet debuted a blonde bob on Instagram and we're officially in a tizzy. Is there a Girls plot line in the making here? Shosh steals Hannah's new 'do? Will she try a blonde doughnut bun? The possibilities are endless.

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